Dear all,

the attached, actually rather obvious patch fixes an issue when
an optional dummy with the value attribute was passed as DIM
argument to the SIZE intrinsic.  Instead of some hand-crafted,
incomplete presence check for the argument, it makes more sense
to rely on gfc_conv_expr_present().

Regtested on x86_64-pc-linux-gnu.  OK for mainline?

Thanks,
Harald